1. Field of the Invention:
The invention in general relates to subscriber cable systems, and particularly to improved apparatus in those systems in which stereo signals are delivered in the FM format.
2. Description of the Prior Art:
In a basic subscriber cable TV system, TV signals are transmitted from headend apparatus via the cable to a plurality of user locations where converter apparatus is operable to condition selected signals for presentation by a TV set.
In addition to this basic service, many cable operators are including transmission of signals within the FM band along with the TV signals. Such FM signals may include regular FM programs, stereo FM programs and simulcast programs in which the sound normally associated with a particular TV program is broadcast and presented in a stereo format as the viewer watches the TV program.
In one prior art system, a user would have to select a TV channel via the converter and then separately tune an associated FM receiver to the proper assigned frequency for simulcast reception, the TV channel and FM frequency assignments being supplied by the cable operator. Any change to a different TV channel would necessitate the additional retuning of the FM receiver as a separate step, or where simulcast reception is not provided on the other channel, the FM receiver would be turned off and the TV's normal audio portion would be turned up for viewer listening.
To obviate the inconvenience of having to separately tune two different units, another prior art apparatus provides for the selection of a TV channel with the simultaneous automatic tuning of an FM receiver apparatus to the proper FM frequency (if any) associated with the particular TV channel selected by the user. This is accomplished with a stereo module unit which includes an FM tuner and a microprocessor which controls the selection of the FM tuner. The microprocessor has an associated read-only-memory an EEPROM for example, into which is stored the individual TV channel numbers and the FM frequencies associated with respective channels, these assignments being designated as a channel map.
A user through a remote control unit enters a desired channel number. Upon reception, the microprocessor identifies the channel number and locates the corresponding FM frequency in the EEPROM and thereafter controls the frequency selection of the FM tuner to this frequency. In the absence of any frequency designation, the microprocessor will control a separate and distinct TV tuner for presentation of the audio portion of the TV picture.
This arrangement works quite satisfactorily as long as there are no changes in the FM frequency assignments. Any change in the channel map, however, would require operator personnel to visit every subscriber in order that the EEPROMs in the stereo module units be updated wih the latest channel map, such updating being accomplished either by a reprogramming or a replacement of the EEPROM.
The present invention obviates this requirement for repeated visits by the cable operator to the individual subscribers in order to accomplish channel map updating.